Beta-agonists are extremely effective as bronchodilators and have been widely used as first line therapy for people with asthma. However, recent studies suggest that long term regular use may contribute to worsening asthma control or increase the risk of death or near death from asthma. Speculation is that bronchodilation may permit continued exposure to antigens and other material that provoke inflammation or because the active agent stimulates inflammation. The National Heart, Lung and Blood Institute's (NHLBI's) Expert Panel on the Management of Asthma recommends that inhaled beta-agonists continue to be used as required for the relief of symptoms, but that anti-inflammatory therapy be instituted in patients who require beta-agonists on a daily basis. Inhaled corticosteroids are the most commonly used anti-inflammatory agents used for chronic therapy. Although increasing use of high-dose inhaled corticosteroid therapy has raised concerns about the potential for adverse effects with long-term use, standard doses of corticosteroids given by inhalation appear to be safe and effect. Beta- agonists are felt to provide symptom relief while inhaled corticosteroids are felt to modify the disease; there is evidence of asthma control even after inhaled corticosteroids are reduced or stopped (off drug effect). A long-acting inhaled beta-agonist, salmeterol induces bronchodilation and may have anti-inflammatory properties. While early studies of the regular use of salmeterol suggest that it reduces the symptomatic severity of asthma, the importance of its bronchodilating versus anti- inflammatory activities is not known. The relative importance of anti-inflammatory versus bronchodilation activity might be inferred by studying the relationship between reductions in inflammatory markers at the completion of the therapy and the rate of recurrence of symptoms after therapy is removed (off drug effect). Symptoms are more likely to recur quickly after therapy with agents having only bronchodilator properties than after therapy with agents that alter the fundamental pathogenesis of the disease. This study will test, in patients with moderate asthma, whether inhaled corticosteroids alone or inhaled long-acting beta-agonist alone or placebo is more efficacious in controlling asthma symptoms and airway function.